On Mon, Nov 24, 2008 at 02:06:33PM -0800, Greg Meredith wrote:
> Now, are there references for a theory of monads and take-out options? For
> example, it seems that all sensible notions of containers have take-out. Can
> we make the leap and define a container as a monad with a notion of
> take-out? Has this been done? Are there reasons for not doing? Can we say
> what conditions are necessary to ensure a notion of take-out?
Yes, you are describing 'co-monads'.
here is an example that a quick web search brought up, and there was a
paper on them and their properties published a while ago
http://www.eyrie.org/~zednenem/2004/hsce/Control.Comonad.html
the duals in that version are
extract - return
duplicate - join
extend - flip (>>=) (more or less)
John
--
John Meacham - ⑆repetae.net⑆john⑈